Hybrid vehicles and electric vehicles are well known to people as eco-friendly vehicles. Typically, a hybrid vehicle is considered as a vehicle having two or more power sources such as an engine and a motor, and an electric vehicle is considered as a vehicle using a battery only.
A hybrid vehicle can generate electricity while the vehicle is running so to charge a battery equipped in the vehicle. Then, the hybrid vehicle transforms stored electrical energy into a motive power for driving. In particular, a hybrid vehicle uses a regenerative braking system to convert the kinetic energy of an electric motor, which rotates in a reverse direction when the vehicle decelerates, into electrical energy. The hybrid vehicle can store the electrical energy into a battery, and uses stored energy during driving in order to increase fuel energy efficiency.
An electric vehicle (EV) uses a high-voltage battery instead of a fossil fuel as well as a motor instead of an engine. The major feature of EVs is that they have a charging operation, which is different from conventional vehicles including an internal combustion engine. A charging system for charging a battery equipped in the vehicle can be implemented in various forms.
As an eco-friendly automobile, there is an electric vehicle as well as a fuel cell electric vehicle (FCEV or FCV) which operates an electric motor by using electrical energy generated by reacting stored hydrogen with oxygen in the air. Because the FCV uses electrical energy generated by reacting hydrogen and oxygen, the FCV may discharge water instead of exhaust gas so that it could be recognized by people as a pollution-free vehicle. Since electric vehicles cannot produce electricity by themselves, they should be charged at a charging facility or a charging station. However, fuel cell vehicles can produce electricity by themselves, so they do not have to be charged with electrical energy at the charging facility or a charging station. The time for injecting hydrogen into the FCV would be not much different from the time for injecting conventional fossil fuels (e.g., gasoline, diesel) into a vehicle, so that the user convenience can be improved.